1. Technical Field
The present invention relates to a non-volatile memory device and, more particularly, to a resistive memory device, a system including the same and a method for fabricating the same.
2. Description of the Related Art
With rapid development of digital telecommunication and electronic appliance technologies, conventional memory devices such as a dynamic random access memory (DRAM) or a flash memory ill soon reach their physical limits in obtaining higher integration and higher device performance. For example, a flash memory representing a non-volatile memory uses a high voltage in programming and erase operations and has physical limits due to interference between adjacent cells in being scaled down. Moreover, the flash memory suffers from a low operating speed and high power consumption. As an alternative to conventional memory devices, different types of memory devices are being developed to store data based on different characteristics such as phase transition, magnetic field variation, and the like as follows. As an example, a phase-change memory device may store information by varying resistance of a material by causing a phase change thereof.
A ferroelectric RAM (FeRAM) has been developed but raises a concern with respect to its material stability. A magnetic RAM (MRAM) has also been developed, but it has a complicated fabrication process, a multilayer structure, and a small reading/writing margin. As an alternative to the above-discussed memory devices, a resistive random access memory (ReRAM) has been developed to store data based on resistance variation of a thin film according to voltage applied to the thin film. Theoretically, the ReRAM does not suffer from deterioration even after numerous writing and erasing operations and exhibits normal operation characteristics even at a high temperature. In addition, the ReRAM exhibits non-volatile properties and provides excellent data stability. Furthermore, the ReRAM operates at a high operation speed of 10 to 20 ns in varying resistance variation of 1000 times or more upon application of an input pulse thereto.
Since a variable resistance layer of the ReRAM device is generally a single layer, the ReRAM can be highly integrated and operate at a high speed. Further, typical integration technologies for complementary metal oxide semiconductor (CMOS) can be applied to the ReRAM. Here, the variable resistance layer is generally formed of an oxide. Specifically, the oxide includes a binary oxide and a perovskite oxide. Recently, the variable resistance layer of the ReRAM is often made of a metal-doped perovskite oxide.
As an example of ReRAM devices, Korean Patent Publication No. 2006-106035 discloses a ReRAM device that includes a resistance layer formed of a Cr-doped perovskite oxide of SrZr3.
Korean Patent Publication No. 2004-63600 discloses a ReRAM device which includes an iridium (Ir) substrate, a barrier layer of Ta, TaN, Ti, TiN, TaAlN, TiSiN, TaSiN, TiAl or TiAlN formed on the substrate, and a Pr0.7Ca0.3MnO3 (PCMO) thin film formed as a resistance layer on the barrier layer.
However, since these memory devices are single level devices which allow a device formed at an intersection of an upper data line and a lower data line to store single on/off information, such memory devices have lower data storage capacity per unit area than multi-level devices.
Therefore, it is useful to have a memory device which may be fabricated through a simple fabrication process without surface contamination, is applicable to various memory devices including non-volatile memory devices, and permits adjustment of various resistance states through control of an operating voltage.